   "Like `let`, except in which the left hand side is a destructuring map, right hand side is the argument to key finder.
   Beside symbols, the destructuring map optionally supports `:defs` (symbols bound to key finders) and `:as` keys.
 
-  ## Example
+  ### Example
 
   ```
   (letval [{:defs [foo bar] ; foo, bar are key finders

  |`:envvar` |Environment variable that can override the config value and system property (before parsing) |
  |`:source` |Source or container (of reference type, e.g. atom/agent/promise etc.) of key/value pairs     |

  ## Lookup function

  ```
  (fn [store key validator description value-parser default-value? default-value not-found-handler])->value

(defn realize-config
  "Realize config by applying variable substitution, if any.

  ### Options

  | Kwarg          | Type   | Description                 | Default                 |
  |----------------|--------|-----------------------------|-------------------------|
